Many formats exist for digitally encoding analog audio signals. For example, analog audio signals can be digitally encoded in a multi-bit format, such as digital pulse-code modulation (PCM). Alternatively, analog audio signals may be digitally encoded in a single-bit format, such as direct stream digital (DSD). A DSD signal may be organized in a PCM frame in a DSD over PCM (DOP) format. Thus, PCM signals and DoP signals may share a similar data structure 100, as illustrated in FIG. 1. For example, audio signals may be encoded and transmitted in a 24-bit PCM frame 102. Similarly, audio signals may be encoded as DoP data and transmitted in the same frame structure 102. In order to distinguish between DoP data and PCM data, each DoP frame may be headed by an 8-bit DSD marker 104, followed by 16 bits of DSD audio data 106. Multiple channels of audio data, such as a left channel and a right channel, may be encoded and transmitted using DoP.
Processing audio-signals encoded in one format with audio processing circuitry for processing of audio signals encoded in another format can cause reproduction of undesirable noise. For example, if multi-bit signals are processed using single-bit audio signal processing circuitry, undesirable noise is reproduced and heard by a user. Likewise, if single-bit audio signals are processed using multi-bit audio signal processing circuitry undesirable noise is reproduced and heard by a user. When the DSD marker 104 of FIG. 1 is processed using circuitry for processing PCM audio signals, undesirable noise is reproduced and heard by a user. Furthermore, switching between processing audio signals of different formats, such as PCM audio signals and DoP audio signals, can create transient artifacts, inducing reproduction of undesirable noise.
Shortcomings mentioned here are only representative and are included simply to highlight that a need exists for improved electrical components, particularly for audio signal processing employed in consumer-level devices, such as mobile phones. Embodiments described herein address certain shortcomings but not necessarily each and every one described here or known in the art. Furthermore, embodiments described herein may present other benefits than, and be used in other applications than, those of the shortcomings described above.